A spark plug including a terminal end, a firing end, an axial centerline extending between the terminal end and the firing end, and an insulative core extending between the terminal end and the firing end. The insulative core includes a central bore coincident with the axial centerline extending through the insulative core, and an insulative nose extending along and symmetrically about the axial centerline from an end surface of the insulative core at the firing end to a transition location along an axial length of the insulative core, wherein a perimeter surface of the insulative nose has a concave curvilinear shape between the end surface and the transition location.

A spark plug including a terminal end, a firing end, an axial centerline extending between the terminal end and the firing end, and an insulative core extending between the terminal end and the firing end. The insulative core includes a central bore coincident with the axial centerline extending through the insulative core, and an insulative nose extending along and symmetrically about the axial centerline from an end surface of the insulative core at the firing end to a transition location along an axial length of the insulative core, wherein a perimeter surface of the insulative nose has a concave curvilinear shape between the end surface and the transition location.

A spark plug with an improved heat-dissipating capacity of the center electrode. The spark plug includes a ground electrode, a center electrode and a ceramic insulator, which is designed to accommodate the center electrode. The center electrode has a center-electrode head which lies in the direction of an electrical connection region of the spark plug and which includes an end face that is in contact with an electrically conductive connection element disposed between the electrical connection region and the center-electrode head. At its outer periphery, the center-electrode head is at least regionally in heat-conducting contact with the ceramic insulator and forms a heat-conducting contact region.

An employed rear mold is comprised of a plurality of mold pieces. The plurality of mold pieces include a first mold piece which forms a first partial internal surface of the internal surface of the rear mold along the entire circumference of the internal surface, and a second mold piece which is located axially forward of the first mold piece and forms a second partial internal surface of the internal surface of the rear mold along the entire circumference of the internal surface. Releasing the molded body includes starting to move the first mold piece rearward in relation to a rear molded portion, and, subsequently to starting to move the first mold piece, starting to move the second mold piece rearward in relation to the rear molded portion, thereby disassembling the rear mold into the plurality of mold pieces.

A spark plug includes a tubular metallic shell, a tubular insulator held in the metallic shell and having an axial hole, a center electrode held at one end of the axial hole, a metallic terminal member held at the other end of the axial hole, and a resistor element disposed between the center electrode and the metallic terminal member in the axial hole and containing glass and an electrically conductive material. The resistor element has a first resistor layer disposed on the center electrode side and closest to the center electrode and containing titanium oxide, and a second resistor layer disposed on the metallic terminal member side in relation to the first resistor layer and whose titanium oxide content is lower than that of the first resistor layer. The titanium oxide content decreases from the center electrode side toward the metallic terminal member side.

A spark plug includes a tubular metallic shell, a tubular insulator held in the metallic shell and having an axial hole, a center electrode held at one end of the axial hole, a metallic terminal member held at the other end of the axial hole, and a resistor element disposed between the center electrode and the metallic terminal member in the axial hole and containing glass and an electrically conductive material. The resistor element has a first resistor layer disposed on the center electrode side and closest to the center electrode and containing titanium oxide, and a second resistor layer disposed on the metallic terminal member side in relation to the first resistor layer and whose titanium oxide content is lower than that of the first resistor layer. The titanium oxide content decreases from the center electrode side toward the metallic terminal member side.

The present disclosure relates to an ignition plug for initiating combustion in a cylinder of a combustion engine, wherein the cylinder can be operated in an active mode and in a deactivated mode. The ignition plug comprises a housing that can be connected to the cylinder, an insulator is fastened to the housing and comprises an axial bore hole and a middle electrode is arranged in the axial bore hole to form an annular gap between the middle electrode and the insulator. The ignition plug comprises a sealing element that can be activated in dependence upon the mode of the cylinder so as to seal the gap preventing any seepage of oil during cylinder deactivation.

A spark plug having an insulating body defining a longitudinal axis and including a base portion and an obstruction portion, a first electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the first electrode extending through the base portion of the insulating body, and a second electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the second electrode extending through the base portion and the obstruction portion of the insulating body, wherein the obstruction portion axially extends beyond the distal portion of the first electrode.

A spark plug includes a cylindrical metallic shell having a ground electrode at a forward end of the cylindrical metallic shell, a cylindrical insulator held in the metallic shell, a center electrode disposed in the insulator, a resistor element disposed in the insulator and having a forward end located rearward of a rear end of the center electrode, a forward-end-side electrically conductive seal layer disposed in the insulator to be located between the center electrode and the resistor element, and a rear-end-side electrically conductive seal layer disposed in the insulator to be located rearward of the resistor element. The forward end of the resistor element is located forward of the rear end of the metallic shell, and the rear end of the resistor element is located rearward of the rear end of the metallic shell.

A spark plug includes a cylindrical metallic shell having a ground electrode at a forward end of the cylindrical metallic shell, a cylindrical insulator held in the metallic shell, a center electrode disposed in the insulator, a resistor element disposed in the insulator and having a forward end located rearward of a rear end of the center electrode, a forward-end-side electrically conductive seal layer disposed in the insulator to be located between the center electrode and the resistor element, and a rear-end-side electrically conductive seal layer disposed in the insulator to be located rearward of the resistor element. The forward end of the resistor element is located forward of the rear end of the metallic shell, and the rear end of the resistor element is located rearward of the rear end of the metallic shell.